The string appears to be a raw file name, likely generated by a digital camera or an automated export system. Because the name itself doesn't refer to a known viral video or specific public event, the most "useful" blog post on this topic would be a technical guide for people who have encountered similar cryptic file names and don't know how to handle them.
Below is a proposed blog post structure focused on . 73691-_1678561465.mp4
The second half of your file name ( 1678561465 ) looks like a . The string appears to be a raw file